php53: fix on darwin

* add libssh2 to build inputs (configure fails without this)
* link with stdc++
* add icu/lib directory to DYLD_LIBRARY_PATH (and wrap binaries with this
  environment variable
* add libiconv to build inputs
* fix --with-iconv configure flag (was --with-iconv-dir which is not a valid
  flag)
php53: add optional pcntl flag
php53: restore nix gd version
php53-xdebug: add expression
update pulseaudio to 4.0 and sbc to 1.1
libcap needs to be a propagated build input for pulseaudio
add retroarch 0.9.9
vim-xdebug: add expression
added mcrypt
Linux 3.4: Doesn't support CONFIG_RC_DEVICES option
Process /etc/fonts/conf.d before upstream fonts/conf.d

Otherwise the user won't be able to override anything specified in
NixOS' /etc/fonts/conf.d, since ~/.config/fontconfig is included from
upstream fonts/conf.5/50-user.conf.
google-talk-plugin: Enable screen sharing
disnix: push to latest 0.3 development release
moderntimeline: Add extra source URL
maintainers: change my attrname to be uniform
liferea: add -- A GTK-based news feed reader
whitespace cleaning
libpng: keep versioning in all-packages.nix, not in individual expressions
libpng: merge apng expression (keep patch disabled by default)

I made sure no rebuild will happen because of this.
Unfortunately this meant merging attrsets instead of just using an
optionalString for postPatch
kde 4.10: option to use a libcanberra with gtk support

by default (as it was before), kde depends on a libcanberra with its
gtk dependency removed so a kde system can be gtk-free.

However, both firefox and chromium depend on gtk+ and libcanberra too.
So this leads to 2 versions being installed. this option combats that
by letting the kde use the other libcanberra